System Namespace Array Class
Searches an entire one-dimensional sorted Array for a specific element, using the IComparable interface implemented by each element of the Array and by the specified object.
[ VB ]
<Serializable>
Overloads Public Shared Function BinarySearch ( _
ByVal array As Array, _
ByVal value As Object _
) As Integer
[ C# ]
[Serializable]
public static int BinarySearch (
Array array,
object value
);
[ C++ ]
[Serializable]
public: static int BinarySearch (
Array* array,
Object* value
);
[JScript ]
public Serializable
static function BinarySearch (
array : Array,
value : Object
) : int;
- array
- The one-dimensional Array to search.
- value
- The object to search for.
The index of the specified value in the specified array, if value is found.
-or-
A negative number, which is the bitwise complement of the index of the first element that is larger than value, if value is not found and value is less than one or more elements in array.
-or-
A negative number, which is the bitwise complement of ( the index of the last element + 1 ) , if value is not found and value is greater than any of the elements in array.
Either value or every element of array must implement the IComparable interface, which is used for comparisons. If the elements of array are not already sorted in increasing value according to the IComparable implementation, the result might be incorrect.
Duplicate elements are allowed. If the Array contains more than one element with the same value, the method returns only one of the occurrences, and it might return any one of the occurrences, not necessarily the first one.
A null reference ( Nothing in Visual Basic ) can always be compared with any other type; therefore, comparisons with a null reference ( Nothing ) do not generate an exception. When sorting, a null reference ( Nothing ) is considered to be less than any other object.
If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator ( ~ ) to a negative result to produce the index of the first element, if any, that is larger than the specified search value.
The following code example shows how to use BinarySearch to locate a specific object in an Array.
[ VB ]
Imports System
Imports Microsoft.VisualBasic
Public Class SamplesArray
Public Shared Sub Main ( )
' Creates and initializes a new Array.
Dim myIntArray As Array = Array.CreateInstance ( GetType ( Int32 ) , 5 )
Dim i As Integer
For i = myIntArray.GetLowerBound ( 0 ) To myIntArray.GetUpperBound ( 0 )
myIntArray.SetValue ( i * 2, i )
Next i
' Displays the values of the Array.
Response.WriteLine ( "The Int32 array contains the following:" )
PrintValues ( myIntArray )
' Locates a specific object that does not exist in the Array.
Dim myObjectOdd As Object = 3
FindMyObject ( myIntArray, myObjectOdd )
' Locates an object that exists in the Array.
Dim myObjectEven As Object = 6
FindMyObject ( myIntArray, myObjectEven )
End Sub
Public Shared Sub FindMyObject ( myArr As Array, myObject As Object )
Dim myIndex As Integer = Array.BinarySearch ( myArr, myObject )
If myIndex < 0 Then
Response.WriteLine ( "The object to search for ( {0} ) is not found. " _
+ "The next larger object is at index {1}.", myObject, Not ( myIndex ) )
Else
Response.WriteLine ( "The object to search for ( {0} ) is at index " _
+ "{1}.", myObject, myIndex )
End If
End Sub
Public Shared Sub PrintValues ( myArr As Array )
Dim myEnumerator As System.Collections.IEnumerator = _
myArr.GetEnumerator ( )
Dim i As Integer = 0
Dim cols As Integer = myArr.GetLength ( ( myArr.Rank - 1 ) )
While myEnumerator.MoveNext ( )
If i < cols Then
i += 1
Else
Response.WriteLine ( )
i = 1
End If
Response.Write ( ControlChars.Tab + "{0}", myEnumerator.Current )
End While
Response.WriteLine ( )
End Sub
End Class
' This code produces the following output.
'
' The Int32 array contains the following:
' 0 2 4 6 8
' The object to search for ( 3 ) is not found. The next larger object is at index 2.
' The object to search for ( 6 ) is at index 3.
[ C# ]
using System;
public class SamplesArray {
public static void Main ( ) {
// Creates and initializes a new Array.
Array myIntArray = Array.CreateInstance ( typeof ( Int32 ) , 5 );
for ( int i = myIntArray.GetLowerBound ( 0 ); i <= myIntArray.GetUpperBound ( 0 ); i++ )
myIntArray.SetValue ( i*2, i );
// Displays the values of the Array.
Response.WriteLine ( "The Int32 array contains the following:" );
PrintValues ( myIntArray );
// Locates a specific object that does not exist in the Array.
Object myObjectOdd = 3;
FindMyObject ( myIntArray, myObjectOdd );
// Locates an object that exists in the Array.
Object myObjectEven = 6;
FindMyObject ( myIntArray, myObjectEven );
}
public static void FindMyObject ( Array myArr, Object myObject ) {
int myIndex=Array.BinarySearch ( myArr, myObject );
if ( myIndex < 0 )
Response.WriteLine ( "The object to search for ( {0} ) is not found. The next larger object is at index {1}.", myObject, ~myIndex );
else
Response.WriteLine ( "The object to search for ( {0} ) is at index {1}.", myObject, myIndex );
}
public static void PrintValues ( Array myArr ) {
System.Collections.IEnumerator myEnumerator = myArr.GetEnumerator ( );
int i = 0;
int cols = myArr.GetLength ( myArr.Rank - 1 );
while ( myEnumerator.MoveNext ( ) ) {
if ( i < cols ) {
i++;
} else {
Response.WriteLine ( );
i = 1;
}
Response.Write ( "\t{0}", myEnumerator.Current );
}
Response.WriteLine ( );
}
}
/*
This code produces the following output.
The Int32 array contains the following:
0 2 4 6 8
The object to search for ( 3 ) is not found. The next larger object is at index 2.
The object to search for ( 6 ) is at index 3.
*/
[JScript ]
import System
import System.Collections
// Creates and initializes a new Array.
var myIntArray : System.Array = System.Array.CreateInstance ( Int32, 5 );
for ( var i : int = myIntArray.GetLowerBound ( 0 ); i <= myIntArray.GetUpperBound ( 0 ); i++ )
myIntArray.SetValue ( Int32 ( i*2 ) , i );
// Displays the values of the Array.
Response.WriteLine ( "The Int32 array contains the following:" );
PrintValues ( myIntArray );
// Locates a specific object that does not exist in the Array.
var myObjectOdd : Object = 3;
FindMyObject ( myIntArray, myObjectOdd );
// Locates an object that exists in the Array.
var myObjectEven : Object = 6;
FindMyObject ( myIntArray, myObjectEven );
function FindMyObject ( myArr : System.Array, myObject : Object ) {
var myIndex : int = System.Array.BinarySearch ( myArr, myObject );
if ( myIndex < 0 )
Response.WriteLine ( "The object to search for ( {0} ) is not found. " +
"The next larger object is at index {1}.", myObject, ~myIndex );
else
Response.WriteLine ( "The object to search for ( {0} ) is at index {1}.", myObject, myIndex );
}
function PrintValues ( myArr : System.Array ) {
var arrEnum : IEnumerator = myArr.GetEnumerator ( );
arrEnum.Reset ( );
while ( arrEnum.MoveNext ( ) ) {
Response.Write ( "{0,-6}", arrEnum.Current.ToString ( ) );
}
Response.WriteLine ( );
}
/*
This code produces the following output.
The Int32 array contains the following:
0 2 4 6 8
The object to search for ( 3 ) is not found. The next larger object is at index 2.
The object to search for ( 6 ) is at index 3.
*/
Array Members Array.BinarySearch Overload List IComparable Sort
